// ImGui GLFW binding with OpenGL3 + shaders
// In this binding, ImTextureID is used to store an OpenGL 'GLuint' texture
// identifier. Read the FAQ about ImTextureID in imgui.cpp.

// You can copy and use unmodified imgui_impl_* files in your project. See
// main.cpp for an example of using this. If you use this binding you'll need to
// call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(),
// ImGui::Render() and ImGui_ImplXXXX_Shutdown(). If you are new to ImGui, see
// examples/README.txt and documentation at the top of imgui.cpp.
// https://github.com/ocornut/imgui

#include "imgui_impl_glfw_gl3.h"
#include <imgui.h>

// GL3W/GLFW
#include <GLFW/glfw3.h>
#ifdef _WIN32
#undef APIENTRY
#define GLFW_EXPOSE_NATIVE_WIN32
#define GLFW_EXPOSE_NATIVE_WGL
#include <GLFW/glfw3native.h>
#endif

// Data
static GLFWwindow *g_Window = NULL;
static double g_Time = 0.0f;
static bool g_MousePressed[3] = {false, false, false};
static float g_MouseWheel = 0.0f;
static GLuint g_FontTexture = 0;

// This is the main rendering function that you have to implement and provide to
// ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure) If text
// or lines are blurry when integrating ImGui in your engine:
// - in your Render function, try translating your projection matrix by
// (0.5f,0.5f) or (0.375f,0.375f)
void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData *draw_data)
{
  // Avoid rendering when minimized, scale coordinates for retina displays
  // (screen coordinates != framebuffer coordinates)
  ImGuiIO &io = ImGui::GetIO();
  int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
  int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
  if (fb_width == 0 || fb_height == 0)
    return;
  draw_data->ScaleClipRects(io.DisplayFramebufferScale);

  // We are using the OpenGL fixed pipeline to make the example code simpler to
  // read! Setup render state: alpha-blending enabled, no face culling, no depth
  // testing, scissor enabled, vertex/texcoord/color pointers.
  GLint last_texture;
  glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
  GLint last_viewport[4];
  glGetIntegerv(GL_VIEWPORT, last_viewport);
  GLint last_scissor_box[4];
  glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
  glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glDisable(GL_CULL_FACE);
  glDisable(GL_DEPTH_TEST);
  glEnable(GL_SCISSOR_TEST);
  glEnableClientState(GL_VERTEX_ARRAY);
  glEnableClientState(GL_TEXTURE_COORD_ARRAY);
  glEnableClientState(GL_COLOR_ARRAY);
  glEnable(GL_TEXTURE_2D);
  // glUseProgram(0); // You may want this if using this code in an OpenGL 3+
  // context

  // Setup viewport, orthographic projection matrix
  glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
  glMatrixMode(GL_PROJECTION);
  glPushMatrix();
  glLoadIdentity();
  glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  glLoadIdentity();

// Render command lists
#define OFFSETOF(TYPE, ELEMENT) ((size_t) & (((TYPE *)0)->ELEMENT))
  for (int n = 0; n < draw_data->CmdListsCount; n++) {
    const ImDrawList *cmd_list = draw_data->CmdLists[n];
    const ImDrawVert *vtx_buffer = cmd_list->VtxBuffer.Data;
    const ImDrawIdx *idx_buffer = cmd_list->IdxBuffer.Data;
    glVertexPointer(2,
        GL_FLOAT,
        sizeof(ImDrawVert),
        (const GLvoid *)((const char *)vtx_buffer + OFFSETOF(ImDrawVert, pos)));
    glTexCoordPointer(2,
        GL_FLOAT,
        sizeof(ImDrawVert),
        (const GLvoid *)((const char *)vtx_buffer + OFFSETOF(ImDrawVert, uv)));
    glColorPointer(4,
        GL_UNSIGNED_BYTE,
        sizeof(ImDrawVert),
        (const GLvoid *)((const char *)vtx_buffer + OFFSETOF(ImDrawVert, col)));

    for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++) {
      const ImDrawCmd *pcmd = &cmd_list->CmdBuffer[cmd_i];
      if (pcmd->UserCallback) {
        pcmd->UserCallback(cmd_list, pcmd);
      } else {
        glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
        glScissor((int)pcmd->ClipRect.x,
            (int)(fb_height - pcmd->ClipRect.w),
            (int)(pcmd->ClipRect.z - pcmd->ClipRect.x),
            (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
        glDrawElements(GL_TRIANGLES,
            (GLsizei)pcmd->ElemCount,
            sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT,
            idx_buffer);
      }
      idx_buffer += pcmd->ElemCount;
    }
  }
#undef OFFSETOF

  // Restore modified state
  glDisableClientState(GL_COLOR_ARRAY);
  glDisableClientState(GL_TEXTURE_COORD_ARRAY);
  glDisableClientState(GL_VERTEX_ARRAY);
  glBindTexture(GL_TEXTURE_2D, (GLuint)last_texture);
  glMatrixMode(GL_MODELVIEW);
  glPopMatrix();
  glMatrixMode(GL_PROJECTION);
  glPopMatrix();
  glPopAttrib();
  glViewport(last_viewport[0],
      last_viewport[1],
      (GLsizei)last_viewport[2],
      (GLsizei)last_viewport[3]);
  glScissor(last_scissor_box[0],
      last_scissor_box[1],
      (GLsizei)last_scissor_box[2],
      (GLsizei)last_scissor_box[3]);
}

static const char *ImGui_ImplGlfwGL3_GetClipboardText(void *user_data)
{
  return glfwGetClipboardString((GLFWwindow *)user_data);
}

static void ImGui_ImplGlfwGL3_SetClipboardText(
    void *user_data, const char *text)
{
  glfwSetClipboardString((GLFWwindow *)user_data, text);
}

void ImGui_ImplGlfwGL3_MouseButtonCallback(
    GLFWwindow *, int button, int action, int /*mods*/)
{
  if (action == GLFW_PRESS && button >= 0 && button < 3)
    g_MousePressed[button] = true;
}

void ImGui_ImplGlfwGL3_ScrollCallback(
    GLFWwindow *, double /*xoffset*/, double yoffset)
{
  g_MouseWheel +=
      (float)yoffset; // Use fractional mouse wheel, 1.0 unit 5 lines.
}

void ImGui_ImplGlfwGL3_KeyCallback(
    GLFWwindow *, int key, int, int action, int mods)
{
  ImGuiIO &io = ImGui::GetIO();
  if (action == GLFW_PRESS)
    io.KeysDown[key] = true;
  if (action == GLFW_RELEASE)
    io.KeysDown[key] = false;

  (void)mods; // Modifiers are not reliable across systems
  io.KeyCtrl =
      io.KeysDown[GLFW_KEY_LEFT_CONTROL] || io.KeysDown[GLFW_KEY_RIGHT_CONTROL];
  io.KeyShift =
      io.KeysDown[GLFW_KEY_LEFT_SHIFT] || io.KeysDown[GLFW_KEY_RIGHT_SHIFT];
  io.KeyAlt = io.KeysDown[GLFW_KEY_LEFT_ALT] || io.KeysDown[GLFW_KEY_RIGHT_ALT];
  io.KeySuper =
      io.KeysDown[GLFW_KEY_LEFT_SUPER] || io.KeysDown[GLFW_KEY_RIGHT_SUPER];
}

bool ImGui_ImplGlfwGL3_CreateFontsTexture()
{
  // Build texture atlas
  ImGuiIO &io = ImGui::GetIO();
  unsigned char *pixels;
  int width, height;
  io.Fonts->GetTexDataAsRGBA32(&pixels,
      &width,
      &height); // Load as RGBA 32-bits (75% of the memory is wasted, but
                // default font is so small) because it is more likely to be
                // compatible with user's existing shaders. If your ImTextureId
                // represent a higher-level concept than just a GL texture id,
                // consider calling GetTexDataAsAlpha8() instead to save on GPU
                // memory.

  // Upload texture to graphics system
  GLint last_texture;
  glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
  glGenTextures(1, &g_FontTexture);
  glBindTexture(GL_TEXTURE_2D, g_FontTexture);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexImage2D(GL_TEXTURE_2D,
      0,
      GL_RGBA,
      width,
      height,
      0,
      GL_RGBA,
      GL_UNSIGNED_BYTE,
      pixels);

  // Store our identifier
  io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;

  // Restore state
  glBindTexture(GL_TEXTURE_2D, last_texture);

  return true;
}

bool ImGui_ImplGlfwGL3_CreateDeviceObjects()
{
  // Build texture atlas
  ImGuiIO &io = ImGui::GetIO();
  unsigned char *pixels;
  int width, height;
  io.Fonts->GetTexDataAsRGBA32(&pixels,
      &width,
      &height); // Load as RGBA 32-bits (75% of the memory is wasted, but
                // default font is so small) because it is more likely to be
                // compatible with user's existing shaders. If your ImTextureId
                // represent a higher-level concept than just a GL texture id,
                // consider calling GetTexDataAsAlpha8() instead to save on GPU
                // memory.

  // Upload texture to graphics system
  GLint last_texture;
  glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
  glGenTextures(1, &g_FontTexture);
  glBindTexture(GL_TEXTURE_2D, g_FontTexture);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexImage2D(GL_TEXTURE_2D,
      0,
      GL_RGBA,
      width,
      height,
      0,
      GL_RGBA,
      GL_UNSIGNED_BYTE,
      pixels);

  // Store our identifier
  io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;

  // Restore state
  glBindTexture(GL_TEXTURE_2D, last_texture);

  return true;
}

void ImGui_ImplGlfwGL3_InvalidateDeviceObjects()
{
  if (g_FontTexture) {
    glDeleteTextures(1, &g_FontTexture);
    ImGui::GetIO().Fonts->TexID = 0;
    g_FontTexture = 0;
  }
}

bool ImGui_ImplGlfwGL3_Init(GLFWwindow *window, bool install_callbacks)
{
  g_Window = window;

  ImGuiIO &io = ImGui::GetIO();
  // Keyboard mapping. ImGui will use those indices to peek into the
  // io.KeyDown[] array.
  io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
  io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
  io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
  io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
  io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
  io.KeyMap[ImGuiKey_PageUp] = GLFW_KEY_PAGE_UP;
  io.KeyMap[ImGuiKey_PageDown] = GLFW_KEY_PAGE_DOWN;
  io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
  io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
  io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
  io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
  io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
  io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
  io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
  io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
  io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
  io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
  io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
  io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;

  // Alternatively you can set this to NULL and call ImGui::GetDrawData()
  // after ImGui::Render() to get the same ImDrawData pointer.
  io.RenderDrawListsFn = ImGui_ImplGlfwGL3_RenderDrawLists;
  io.SetClipboardTextFn = ImGui_ImplGlfwGL3_SetClipboardText;
  io.GetClipboardTextFn = ImGui_ImplGlfwGL3_GetClipboardText;
  io.ClipboardUserData = g_Window;
#ifdef _WIN32
  io.ImeWindowHandle = glfwGetWin32Window(g_Window);
#endif

  if (install_callbacks) {
    glfwSetMouseButtonCallback(window, ImGui_ImplGlfwGL3_MouseButtonCallback);
    glfwSetScrollCallback(window, ImGui_ImplGlfwGL3_ScrollCallback);
    glfwSetKeyCallback(window, ImGui_ImplGlfwGL3_KeyCallback);
  }

  return true;
}

void ImGui_ImplGlfwGL3_Shutdown()
{
  ImGui_ImplGlfwGL3_InvalidateDeviceObjects();
  ImGui::Shutdown();
}

void ImGui_ImplGlfwGL3_NewFrame()
{
  if (!g_FontTexture)
    ImGui_ImplGlfwGL3_CreateDeviceObjects();

  ImGuiIO &io = ImGui::GetIO();

  // Setup display size (every frame to accommodate for window resizing)
  int w, h;
  int display_w, display_h;
  glfwGetWindowSize(g_Window, &w, &h);
  glfwGetFramebufferSize(g_Window, &display_w, &display_h);
  io.DisplaySize = ImVec2((float)w, (float)h);
  io.DisplayFramebufferScale = ImVec2(
      w > 0 ? ((float)display_w / w) : 0, h > 0 ? ((float)display_h / h) : 0);

  // Setup time step
  double current_time = glfwGetTime();
  io.DeltaTime =
      g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f / 60.0f);
  g_Time = current_time;

  // Setup inputs
  // (we already got mouse wheel, keyboard keys & characters from glfw callbacks
  // polled in glfwPollEvents())
  if (glfwGetWindowAttrib(g_Window, GLFW_FOCUSED)) {
    double mouse_x, mouse_y;
    glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
    io.MousePos = ImVec2((float)mouse_x,
        (float)mouse_y); // Mouse position in screen coordinates (set to -1,-1
                         // if no mouse / on another screen, etc.)
  } else {
    io.MousePos = ImVec2(-1, -1);
  }

  for (int i = 0; i < 3; i++) {
    io.MouseDown[i] = g_MousePressed[i]
        || glfwGetMouseButton(g_Window, i)
            != 0; // If a mouse press event came, always pass it as "mouse held
                  // this frame", so we don't miss click-release events that are
                  // shorter than 1 frame.
    g_MousePressed[i] = false;
  }

  io.MouseWheel = g_MouseWheel;
  g_MouseWheel = 0.0f;

  // Hide OS mouse cursor if ImGui is drawing it
  glfwSetInputMode(g_Window,
      GLFW_CURSOR,
      io.MouseDrawCursor ? GLFW_CURSOR_HIDDEN : GLFW_CURSOR_NORMAL);

  // Start the frame
  ImGui::NewFrame();
}
